Electromagnetic heating for vitrification

ABSTRACT

Embodiments disclosed herein include methods and systems for melting or augmenting a melt rate of material in a melter using electromagnetic radiation with a frequency between 0.9 GHz and 10 GHz. In some examples, a power and/or frequency of radiation used may be selected so as to control a temperature of a cold cap in the melter while maintaining emissions from the melter below a threshold level. In this manner, examples described herein may provide for efficient and safe melting and vitrification of radioactive wastes.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No. 16/347,993 filed May 7, 2019, issued as U.S. Pat. No. 11,232,879 on Jan. 25, 2022, which is a 35 U.S.C. 371 National Stage Application of PCT Application No. PCT/US2017/060416 filed Nov. 7, 2017, which claims the benefit under 35 U.S.C. 119 of the earlier filing date of U.S. Provisional Application No. 62/418,445 filed Nov. 7, 2016, the entire contents of which are incorporated by reference, in their entirety, for any purpose.

BACKGROUND

The challenge of isolating radioactive waste from the environment is very formidable. Radioactive waste can be melted into a glass mixture to isolate the radioactive material in the glass mixture. Such isolation can prevent the radioactive material within the glass mixture from entering the environment.

Melters, such as joule heated melters, melt material to form a molten bath. The material in the molten bath may be drained out of the melter and disposed of. The melters may utilize joule heating to melt the material. The molten bath may have a cold cap on an upper surface thereof;.

SUMMARY

Embodiments disclosed herein relate to methods and systems for controllably augmenting the rate of incorporation of material into a molten bath using electromagnetic radiation in a range of 0.9 GHz and 10 GHz.

An example system is disclosed. The example system includes a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid. The example system includes an electromagnetic radiation source located outside of the processing chamber and configured to selectively generate electromagnetic radiation with a frequency between 0.9 GHz and 10 GHz. The example system includes one or more waveguides operably coupled to the electromagnetic radiation source and configured to guide the electromagnetic radiation into the cold cap of the hot material in the processing chamber. The example system includes a controller operably coupled to the electromagnetic radiation source, wherein the controller is configured to selectively adjust one or more of the power or the frequency of the electromagnetic radiation to selectively control a temperature profile in the cold cap while preventing emissions of volatile components from the cold cap from exceeding a selected level.

An example method for melting material is disclosed. The example method includes producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz. The example method includes directing the electromagnetic radiation into the cold cap wherein producing electromagnetic radiation outside of the processing chamber and directing the electromagnetic radiation into the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap without causing emissions of one or more components of the hot material in the cold cap to exceed a selected level.

Another example method for melting material is disclosed. The example method includes producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, wherein the cold cap includes a solid portion that is uppermost in the cold cap and a calcined portion disposed between the solid portion and the molten portion, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz. The example method includes guiding the electromagnetic radiation into the processing chamber. The example method includes directing the electromagnetic radiation into the calcined portion of the cold cap. The example method includes sensing a temperature of the cold cap. The example method includes adjusting one or more of the frequency or power of the electromagnetic radiation responsive to the temperature of the cold cap.

Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, wherein identical reference numerals refer to identical or similar elements or features in different views or embodiments shown in the drawings.

FIG. 1 is a schematic of a system for melting material, according to at least some embodiments.

FIG. 1A is a schematic of an example collimating device, according to at least some embodiments.

FIG. 1B is a schematic of an example collimating device, according to at least some embodiments.

FIG. 2 is a flow chart of a method for melting material, according to at least some embodiments.

FIG. 3 is flow chart of a method for melting a material, according to at least some embodiments.

FIG. 4 is a schematic of a mobile system for melting material, according to at least some embodiments.

FIG. 5 is a schematic of a controller for executing any of the methods disclosed herein, according to an embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The challenge of isolating radioactive waste from the environment is very formidable. New technology is needed to reduce the time and cost for addressing this need. For example, in the United States there is an urgent need to accelerate the vitrification of radioactive defense waste, such as at the Department of Energy Hanford site.

Examples of methods and systems herein may address an urgent need to accelerate the processing rate in melters (e.g., joule-heated melters) that are employed for waste vitrification (e.g., melting radioactive waste and vitrifying the same in a highly stable glass). It is estimated that using present technology, vitrification of present stocks of radioactive waste will take many decades under even the most optimistic assumptions. For example, the processing rate in joule heated melters is limited by the amount of heating at the interface of the newly added material that has not melted (the “cold cap”) and the molten material in the melter. This is because the primary mode of thermal energy transfer into the cold cap is conduction from the molten glass pool below the cold cap. Additional heating may be needed at this interface in order to remove this processing rate limitation. However, it may also be necessary to prevent overheating of the cold cap and not increase the desired bulk average temperature of the glass bath to prevent and/or reduce emission of radioactive material from the surface of the cold cap that faces the plenum of the processing chamber of the melter.

Examples of methods and systems herein utilize electromagnetic energy (e.g., microwave radiation) to aid in melting the material (e.g., waste material and glass particles) in the cold cap. For example, examples of methods and systems described herein direct electromagnetic radiation into the cold cap to the interface between the cold cap and the molten material to accelerate heating subsurface portions of the cold cap. In some examples, the electromagnetic radiation is controlled to penetrate to a selected depth within the cold cap to aid melting/vitrification of waste material in the hot material. For example, the electromagnetic radiation may supplement the heat in a joule heated melter so as to accelerate heating of the cold cap and increase the processing rate of new material without causing emissions of radioactive material from the surface of the cold cap to exceed a selected level.

Example methods and systems described herein may accelerate melting of the cold cap (e.g., incorporation of the cold cap into the molten material) without raising the temperature of the material on the surface (e.g., surface opposite the molten material) of the cold cap above a volatilization temperature of the material or without raising the bulk average temperature of the molten glass bath. Thus, the examples of methods and systems disclosed herein may allow for faster vitrification of material into a molten bath than conventional melters while preventing volatilization (e.g., vaporization) of the material. Accordingly, radioactive materials may be quickly and safely processed (e.g., vitrified) to isolate the radioactive materials from the environment.

FIG. 1 is a schematic of a system 100 for melting material, according to an embodiment. The system 100 includes a processing chamber 110, an electromagnetic radiation source 120, one or more waveguides 122, a waste inlet 130, and a controller 140 operably coupled to the electromagnetic radiation source 120 and the waste inlet 130. The processing chamber 110 may include a container with a wall thickness and material composition sufficient to contain a molten material therein. For example, the processing chamber 110 may include a waste processing chamber (e.g., melter), such as a radioactive waste processing chamber. The processing chamber 110 may include an interior region 112 to contain a hot material 132 therein. For example, the processing chamber 110 may include a refractory metal lining disposed within a housing (e.g., ceramic body). In some examples, the processing chamber may have a relatively long shallow design to aid volumetric heating from the electromagnetic radiation source 120.

The hot material 132 may include a waste material such as radioactive waste or any other material to be incorporated into a molten glass. The hot material 132 may initially include the waste material, one or more solvents (such as an acid), and one or more dissolved portions of the waste material. The hot material 132 may include a slurry of the waste material and the one or more solvents. The hot material 132 may include glass particles for forming a molten glass bath (e.g., molten portion 139), such as borosilicate glass beads or any other glass suitable for vitrifying (radioactive) materials. For example, the slurry may include the glass particles. The molten glass may incorporate or encapsulate (e.g. vitrify) the waste materials therein upon melting. Accordingly, the waste material in the hot material 132 may be vitrified using the system 100.

The hot material 132 may be processed in the processing chamber 110 to include a molten portion 139 and a cold cap 134 disposed on the molten portion 139. The cold cap 134 may be at least semi-solid, and includes an uppermost solid portion 136 and a lower calcined portion 138 below the solid portion 136. The calcined portion 138 may have an interface with the molten portion 139 where the calcined portion 138 is melted into the molten portion 139. For example, incorporation of the cold cap 134 into the molten portion 139 (e.g., melting the hot material) may include at least three distinct processing zones, the solid portion 136 where drying of the hot material 132 occurs (e.g., liquid components of the waste slurry are evaporated); the calcined portion 138 where calcining and other reactions of the components of the hot material takes place; and melting and dissolution of the calcined portion 138 into the larger molten portion 139 (e.g., glass bath) takes place. The primary mode of thermal energy transfer into the cold cap 134 is conduction from the molten portion 139 (e.g., molten glass bath) below the cold cap 134. This conduction is the rate limiting step of the incorporation (e.g., melting) of the unmelted material (cold cap) into the molten portion 139. There may also be accumulation of a gas layer or bubbles at the interface of the cold cap 134 and the molten portion 139 further limiting thermal energy transfer into the cold cap 134. If bubbles are present, localized heating of the cold cap 134 directly above the bubble layer would also increase thermal energy transfer into the cold cap 134.

Additional heating may be needed at the interface of the calcined portion 138 and the molten portion 139 in order to remove this processing rate limitation. However, it may be desirable to only enhance melting and dissolution as this may be the rate limiting step in melting, such as in a joule-heated or induction-heated melter process. Applying excess heat to the solid portion 136 or the calcined portion 138 could result in higher volatilization of hot material (e.g., waste feed components) into gas phase within the processing chamber 110 which may be unintentionally removed or vented with other gas phase constituents within the processing chamber to prevent overpressure. Increasing the bulk temperature of the molten portion 139 may increase the wear of melter components such as the refractory lining and electrodes that supply the electric current into the molten portion 139. It may be desirable to prevent overheating of the cold cap 134 and thereby prevent and/or reduce emission of waste material (e.g., radioactive material) from the surface of the cold cap 134 that faces the plenum (e.g., unfilled space of the interior region 112) of the processing chamber 110. Using a directed beam of electromagnetic radiation can provide the localized heating in the interface region between the calcined portion 138 bottom of the cold cap 134 and the surface of the molten portion 139 (e.g., glass bath). The localized beam may have high enough frequency to concentrate most of the heating in the cold cap but be a low enough frequency to prevent volatilization of the cold cap due to overheating of the upper surface of the cold cap. The molten glass in the molten portion 139 may be conductive and may readily absorb the electromagnetic radiation to rapidly heat. Accordingly, the frequency of the electromagnetic radiation may be limited to prevent penetration of the electromagnetic radiation into molten glass bath to prevent emissions of volatilized waste material caused by overheating of the molten glass bath.

The electromagnetic heating systems can be used with melters where one or both of joule heating or induction heating is used to heat the molten material and the electromagnetic radiation (e.g., microwave) heating power is less than the joule heating or induction heating power because the volume of material in the cold cap is much less than the volume of molten material. For example, the volume of the hot material in the cold cap may be less than one tenth, one eighth, one fifth, one quarter, or one third of the volume of the material in the molten portion.

The electromagnetic radiation source 120 generates and emits electromagnetic radiation at various frequencies, such as 0.9 GHz to 10 GHz, 0.9 GHz to 3 GHz, 3 GHz to 6 GHz, 6 GHz to 10 GHz, 0.9 GHz to 5 GHz, or 5 GHz to 10 GHz. The frequency may be preset or may be varied during processing. Under certain circumstances, the electromagnetic radiation heating range may extend to the 10 GHz to 30 GHz microwave range. In some examples, the electromagnetic radiation source 120 may include a microwave generator or emitter. An advantage of the systems disclosed herein is that there are electromagnetic radiation generators (e.g., microwave generators) in the 0.9 GHz to 10 GHz frequency range which provide a relatively low cost radiation source and for which there is a large amount of commercial experience. The electromagnetic radiation source 120 may emit one or more (e.g., varying) frequencies of the electromagnetic radiation during a discrete duration, such as in one or more of any of the ranges disclosed above. The electromagnetic radiation source 120 may be positioned outside of the processing chamber 110. For example, in examples where the processing chamber is a radioactive waste processing chamber, the life of the electromagnetic radiation source 120 can be prolonged by shielding the electromagnetic radiation source 120 from harmful radiation (e.g. from the radioactive materials) inside of the processing chamber 110. In some examples, the electromagnetic radiation source 120 may be isolated from the radiation in the processing chamber 110 by shielding (of the processing chamber) and by one or more bends in the one or more waveguides. The electromagnetic radiation source 120 generates and emits electromagnetic radiation at various powers, such as 1 kW to 700 kW, 2 kW to 600 kW, 2 kW to 40 kW, 3 kW to 30 kW, 10 kW to 100 kW, or 20 kW to 600 kW. The power may be preset or may be varied during processing.

By controlling the power or frequency of the electromagnetic radiation, the penetration depth of the electromagnetic radiation may be selectively customized to reach into and through the calcined portion 138 to the interface between the molten portion 139 and the calcined portion 138. For example, in the frequency range of 0.9 GHz to 10 GHz, the penetration lengths of the electromagnetic radiation can be more than ten times greater than those in the millimeter wave frequency range and can be well matched to penetrate a selected depth into a cold cap. For example, the penetration depth can be 1 cm or more, such as 1 cm to 20 cm, 1 cm to 3 cm, 3 cm to 6 cm, 6 cm to 10 cm, 10 cm to 15 cm, 15 cm to 20 cm, 1 cm to 15 cm, 1 cm to 5 cm, or 5 cm to 10 cm, 5 cm to 15 cm, more than 2 cm, more than 5 cm, less than 20 cm, less than 10 cm, or less than 5 cm. Moreover, since the penetration depth can be increased by around a factor of ten as the frequency is decreased from 10 GHz to 0.9 GHz, the systems and methods herein provide capability for selective adjustment of penetration depth for different processing conditions or hot materials.

Radiation in the 0.9 GHz to 10 GHz frequency range is well suited to obtaining desired penetration lengths in the 1 cm to 10 cm range in water-soaked cold caps. Such radiation may also be well suited to penetrating to the selected penetration depths in cold caps with little to no water content. The selected penetration depth may be adjusted by choice of the electromagnetic radiation power or frequency. For example, as the frequency is decreased, the penetration depth will increase. When there is a relatively lower water content in the hot material it may be advantageous to use electromagnetic radiation in the 10 GHz to 30 GHz range, such as 10 GHz to 20 GHz, 20 GHz to 30 GHz, 10 GHz to 20 GHz, 10 GHz to 25 GHz, less than 30 GHz, less than 25 GHz, or less than 20 GHz.

Examples of systems and methods described herein may selectively control the frequency, power, and other parameters of electromagnetic radiation heating, including the water content of the radioactive material that is introduced to the processing chamber (e.g., melter), so as to selectively control and increase the processing rate while keeping cold cap surface emissions at a sufficiently low level (e.g., below a threshold level). For example, electromagnetic (e.g., microwave) heating may be used to increase the processing rate of melting in a processing chamber, such as a joule-heated melter or an induction-heated melter, while limiting surface heating of the cold cap 134 to limit or prevent surface emissions of material therefrom. The electromagnetic radiation heating can be employed on existing melters (e.g., systems) as well as on new melters.

Examples of systems and methods disclosed herein may overcome limitations of utilizing directed beams of higher frequency (e g , millimeter) wave electromagnetic radiation to aid in melting the hot material. For example, because of the relatively short wavelength of the electromagnetic radiation in the 30 GHz to 300 GHz range, it may have a penetration depth in the cold cap that is much shorter than the thickness of the cold cap 134, especially if there is a substantial water content in the hot material (e.g., waste). Accordingly, electromagnetic radiation in the 30 GHz to 300 GHz range can cause excess heating at the surface of the cold cap. This can result in poor heating of the cold cap 134 at the interface with the molten portion 139 and elevated emissions of one or more components of the hot material 132 from the surface of the cold cap 134 (that faces the plenum of the processing chamber 110). The relatively short penetration depth of the electromagnetic radiation with the frequency of 30 GHz to 300 GHz can be due to the chemistry of the cold cap and/ or the presence of water therein.

Examples of systems and methods disclosed herein may overcome the limitations of bubbling gas through the molten portion to heat the interface between the cold cap and the molten portion. For example, utilizing electromagnetic radiation in a frequency range of 0.9 GHz to 10 GHz as disclosed herein does not cause emission of material from the surface of the cold cap, whereas bubbling gas through the molten portion causes volatilization and carries one or more components of the hot material 132 (e.g., radioactive waste material) to be carried in the bubbling gas. The example electromagnetic (e.g., microwave) heating systems and methods described here can achieve cold cap-modification enabled processing rate enhancement without the issues that have prevented rate enhancement attainment by bubbling and could thereby increase the processing rate of hot material therein by a factor of three or more for a joule heated melter.

The electromagnetic radiation 125 may be directed into the interior region 112 of the processing chamber 110 via one or more waveguides 122. For example, the one or more waveguides may be operably coupled to the electromagnetic radiation source 120. The one or more waveguides may guide the electromagnetic radiation into the cold cap 134 of the hot material in the processing chamber 110. For example, each of the one or more waveguides 122 may include a conduit with one or more bends therein. The conduit may have a circular, square, or rectangular cross-sectional profile. The conduit may have one or more bends or curves therein. An advantage of using microwaves (e.g., electromagnetic radiation in the 0.9 GHz to 10 GHz range) may be that the requirement on window material in the waveguides would be less demanding than in the millimeter radiation frequency range (e.g., 30 GHz to 300 GHz radiation). For example, the window could be made of ceramic rather than a diamond. In some examples, the one or more waveguides may be translatable, such as being movable in one or more of lateral, vertical, or angular direction.

In examples, the system 100 may include one or more collimating devices 124 operably coupled to the one or more waveguides 122. The one or more collimating devices 124 may collimate and direct (e.g., guide) the electromagnetic radiation 125 into one or more beams. For example, the one or more collimating devices 124 may direct the electromagnetic radiation 125 at one or more selected portions of the hot material 132 (e.g., interface below the cold cap 134). The one or more collimating devices 124 may collimate the electromagnetic radiation 125 to a selected beam width. FIG. 1A is a schematic of an example collimating device. As shown, the one or more collimating devices 124 may include a horn 124 a , such as a radiative horn. FIG. 1B is a schematic of an example collimating device. As shown, the one or more collimating devices 124 may include a phased array 124 b . The horn 124 a or phased array 124 b may direct the electromagnetic radiation 125 at one or more discrete portions of the hot material 132 (e.g., the interface of the cold cap 134 and the molten portion 139). In some examples, the electromagnetic radiation generator could use a frequency source in combination with a klystron amplifier system which could send the electromagnetic radiation (e.g., microwave radiation) into a phased array of waveguides that would protrude into the processing chamber.

Returning to FIG. 1, with use of example systems and methods disclosed herein, electromagnetic radiation (e.g., microwave radiation having a frequency of 0.9 GHz to 10 GHz) can be introduced into the processing chamber 110 with a significant amount of collimation and spatial localization. For example, the one or more waveguides 122 and one or more collimating devices 124 may provide localized and directed heating of a selected discrete portion (e.g., the interface between the calcined portion 138 and the molten portion 139) of the hot material 132.

The system 100 includes the controller 140. The controller 140 may be operably coupled to one or more components of the system 100 via one or more connections 144 (e.g., wireless or hardwired connections) to control the system 100. The controller 140 may be operably coupled to the electromagnetic radiation source 120 and the waste inlet 130 via the connections 144. The controller 140 may be used to selectively adjust one or more of the power or the frequency of the electromagnetic radiation to selectively control a temperature profile in the cold cap while preventing emissions of volatile components from the cold cap from exceeding a selected level (e.g., below a threshold level). For example, the controller 140 may direct the electromagnetic radiation source 120 to initiate generation or alter the power or frequency of the electromagnetic radiation 125. For example, the controller 140 may cause the electromagnetic radiation source 120 to vary the power or frequency of electromagnetic radiation 125 emitted into and at least partially through the cold cap 134 during a selected duration. For example, the controller 140 may direct the electromagnetic radiation source 120 to vary the power or the frequency of the electromagnetic radiation 125 every second or more (e.g., 1 second, 10 seconds, 30 seconds, 1 minute, 10 minutes, 3 minutes, etc.). The controller 140 be operably coupled to the waveguide or the one or more collimating devices. In such examples, the controller 140 may control the waveguide or the one or more collimating devices to direct the electromagnetic radiation to a selected depth or lateral location within the processing chamber 110. The controller 140 may actively control the target location of the electromagnetic radiation to coincide with a dry section of the cold cap, or a newly added portion of the hot material. For example, the controller 140 may cause the waveguide and the one or more collimating devices to direct the electromagnetic radiation to move locations in the cold cap, such as to an untreated area of the cold cap.

The controller 140 can use preset or vary characteristics of the electromagnetic radiation such as electromagnetic radiation power or frequency, amount of drying of the hot material in the cold cap; processing rate; or spatial positioning of the electromagnetic radiation using sensed information that such as cold cap temperature, molten material temperature, and emissions of material from the cold cap. Sensed information on material emissions from the cold cap can be used to keep radioactive material emissions from the melting/vitrification process below selected levels. The controller 140 can use closed loop or real time monitoring of these and other parameters and/or open loop control using a look-up table. The look-up table can make use of experimental measurements of the impact of microwave power, frequency, and other parameters on processing rate enhancement, emissions from the cold cap and other characteristics of melter operation.

In examples, the system 100 may include one or more sensors 150 positioned to sense a temperature of one or more portions of the hot material 132 (e.g., the cold cap 134). The one or more sensors 150 may include a millimeter wave pyrometer, a scanning (e.g., infrared) thermometer, a laser thermometer, a thermocouple, or any other suitable temperature sensor. The one or more sensors 150 may include radiation detectors (e.g., Geiger counter) or spectrometers (e.g., atomic absorption spectrometer, inductively coupled plasma atomic emission spectrometer), or any other suitable sensor for detecting the presence or amount of a specific material. The one or more sensors may be positioned to measure a volatile material (e.g., cesium or technetium) in gases emitted from the processing chamber (e.g., from the cold cap). The one or more sensors 150 may be positioned to measure the temperature of the surface of the cold cap 134, chemical emissions of one or more components from the cold cap 134, or the temperature of emissions from the cold cap 134. The one or more sensors 150 may be operably coupled to the controller 140. The controller 140 may receive the sensed temperature from the one or more sensors 150 (e.g., of the cold cap) and responsive thereto, selectively adjust one or more of the power or the frequency of the electromagnetic radiation, such as to maintain a selected penetration depth of the electromagnetic radiation or a selected material processing (e.g., melting) rate. Such selective control can be according to one or more operational programs stored in the controller 140.

In examples, the system 100 may include one or more joule heating electrodes 160 positioned to heat the molten portion 139. For example, one or more joule electrodes 160 may be positioned in the lower region of the processing chamber 110 to heat the molten portion 139 to a selected temperature (e.g., maintain the molten material in a molten state). The processing chamber 110 may be a joule heated melter. The one or more joule heating electrodes 160 may melt the hot material and vitrify the waste in the hot material or maintain the hot material in a molten state where the heating is provided by the passage of current between the joule heating electrodes 160. The one or more joule heating electrodes 160 may be operably coupled to the controller 140. The controller 140 may direct the joule heating electrodes 160 to heat the molten portion 139 in the processing chamber 110 to a selected temperature.

In examples, the system 100 may include one or more induction heating elements 180, such as an induction coil or electromagnet disposed about one or more portions of the processing chamber 110 (e.g., the lower region). The induction coil or electromagnet may be operably coupled to an electronic oscillator. The one or more induction heating elements may be operably coupled to the controller 140. The controller 140 may direct the induction heating elements to heat the molten portion 139 in the processing chamber 110 to a selected temperature.

In examples, the controller 140 may be operably coupled to the waste inlet 130. The controller 140 may control the flow rate of the hot material 132 into the processing chamber 110. For example, the controller 140 may increase or decrease the flow rate of hot material 132 into the processing chamber 120 to achieve a selected processing rate, a cold cap thickness, or a penetration depth of the electromagnetic radiation into the cold cap. The controller 140 may be operably coupled to a pre-dryer (e.g., evaporator or heater) to control pre-drying of the hot material that is introduced into the processing chamber (e.g., melter) based on one or more of temperature or emissions detected by the one or more sensors 150.

The system 100 may include an outlet 170 for removing the molten material (e.g., vitrified waste) from the processing chamber 110. For example, the outlet 170 may be located in the bottom of the processing chamber 110. The outlet 170 may be operably coupled to the controller 140. The outlet 170 may be selectively opened, closed, or partially restricted to control the rate of removal of the molten material therefrom.

The system 100 may include a gas vent 175 for removing gasses from the processing chamber 110. For example, the gas vent 175 may be located in upper portion of the processing chamber 110. The gas vent 175 may be used to remove steam, volatilized components of the waste material, or any other process gases. The gas vent 175 may be operably coupled to the controller 140. The gas vent 175 may be selectively opened, closed, or partially restricted to control the rate of removal of one or more gasses from the processing chamber 110. The gas vent 175 may be operably coupled to a downstream gas cleaning apparatus, such as an apparatus for cleaning one or more chemicals or radioactive materials from the one or more gases.

In examples, the system 100 may include a containment structure 190, such as cladding or shielding to contain one or more emissions from the processing chamber 110. For example, the containment structure 190 may include a sealed enclosure disposed about one or more portions of the system 100. The containment structure 190 may prevent leaks of fluids (e.g., off gasses) and/or radioactivity from the system 100. In some examples, the containment structure 190 may include lead, depleted uranium, depleted thorium, barium sulfate, tungsten, iron, alloys of any of the foregoing, or high density concrete typically used in radioactive processing facilities.

The system 100 may include a power source (not shown). The power source may be operably coupled to any of the components of the system 100 to supply electrical energy thereto. The power source may include at least one of a motor, generator, batteries, solar cells, or any other source of electrical energy.

The electromagnetic generation devices, waveguides, collimating devices, controllers, and other components of the example systems disclosed herein can be used on existing melters or on new melters. For example, the electromagnetic generation devices, waveguides, collimating devices, controllers, and other components of the example systems disclosed herein can be retrofit onto existing waste melters.

In examples, the electromagnetic radiation source can serve as the sole source of heating. Such examples can be of particular interest for small melters with molten bath depths in a range of 1 cm to 15 cm. For example, low volume melters for processing radioactive material may be used where the volume of fissile material (e.g., barium, cesium, iodine, strontium, technetium, xenon, etc.) being melted is limited in order to avoid a critical mass that would result in a nuclear criticality event.

The system described here could increase the waste processing rate of a joule heated melter by a factor of at least two and possibly greater than four.

FIG. 2 is a flow chart of a method 200 for melting material, according to an embodiment. The example method 200 includes an act 210 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz and an act 220 of directing the electromagnetic radiation into the cold cap, wherein producing electromagnetic radiation outside of the processing chamber and directing the electromagnetic radiation into the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap without causing emissions of one or more components of the hot material in the cold cap to exceed a selected level. In some examples, the method 200 may be performed using any components of the system 100.

The act 210 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz may include producing electromagnetic radiation with any suitable electromagnetic radiation generator device such as a microwave radiation generator. The electromagnetic radiation generator may be located outside of the processing chamber as described above with respect to FIG. 1. The act 210 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein may include producing electromagnetic radiation with a frequency of 0.9 GHz to 10 GHz, such as in any of the frequency ranges disclosed herein. The act 210 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein may include producing electromagnetic radiation with a varying frequency between 0.9 GHz and 10 GHz. The act 210 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein may include producing electromagnetic radiation with a varying power between 20 kW and 600 kW.

In examples, producing electromagnetic radiation outside of a processing chamber and directing the electromagnetic radiation into the cold cap of the hot material are effective to cause the electromagnetic radiation to heat the calcined portion of the cold cap without heating the solid portion to a temperature in excess of a vaporization temperature of the hot material (e.g., the waste material or glass particles therein).

One or more of the frequency or power level of the electromagnetic radiation may be such that the surface temperature of the newly added material is maintained at or adjusted to at least 90° C., such as less than 150° C. when liquid is present on the cold cap surface for borosilicate glass typically used for vitrifying radioactive waste materials. The temperature ranges may vary depending on the composition of the hot material slurry being fed to the processing chamber (e.g., melter). For portions of the cold cap that are dry and free of liquids, the temperature can be locally raised to higher temperatures in the range of 150° C. to 500° C., or greater. One or more of the frequency or power level of the electromagnetic radiation should be such as to keep surface emissions of the hot material (e.g., cold cap) below a selected level (e.g., below a threshold level), such as where volatilization of radioactive species (e.g., barium, cesium, iodine, strontium, technetium, xenon, etc.) are limited to below the selected level or even prevented.

Producing the electromagnetic radiation may include producing the electromagnetic radiation at a power level (or power supplied to the electromagnetic radiation generator) effective to cause heating of one or more portions of the cold cap without over heating the cold cap to cause emissions of one or more components of the hot material to exceed a selected level. The power level may be controlled by a controller. The power level may be controlled responsive to sensed information, such as temperature of the cold cap, emissions from the cold cap, feed rate of the hot material, etc. A suitable level power of the electromagnetic radiation to heat the cold cap without causing emissions above the selected level may be preset or vary depending upon on one or more of the geometry of the processing chamber, the chemical composition of the hot material, the thickness of the cold cap, the thickness of the molten material, an acceptable level of emissions of the one or more components, the dryness of the hot material, the frequency of the electromagnetic radiation, the temperature of the cold cap, the temperature of the molten portion, etc. The suitable level of power may include any of the levels of power disclosed herein, such as 2 kW to 600 kW.

Producing the electromagnetic radiation may include producing the electromagnetic radiation at a power level effective produce a selected penetration depth of electromagnetic radiation into the cold cap, such as in the range of 1 cm to 15 cm.

In examples, the selected level of emissions of the one or more components of the hot material (e.g., cesium, technetium, etc.) may depend on one or more of the chemical composition of the hot material, the species of the one or more components of the hot material that is emitted, the rate of processing of the hot material, the amount of hot material in the processing chamber, the duration of time that the hot material resides in the processing chamber, the power of the electromagnetic radiation applied to the hot material, the frequency of the electromagnetic radiation applied to the hot material, environmental regulations, safety standards, etc. The selected level may be based on a rate of emission, such as parts per million per minute or hour.

The act 220 of directing the electromagnetic radiation into the cold cap without causing volatilization of the hot material in the cold cap may include directing the electromagnetic radiation into the cold cap with one or more waveguides. For example, one or more waveguides may be operably coupled to the electromagnetic radiation generator and protrude to (e.g., into) the interior region of the processing chamber. In some examples, directing the electromagnetic radiation into the cold cap without causing volatilization of the hot material in the cold cap may include directing the electromagnetic radiation into cold cap into the calcined portion of the cold cap, such as to the interface between the calcined portion and the molten portion of the hot material in the processing chamber.

In examples, directing the electromagnetic radiation into the cold cap without causing volatilization of the hot material in the cold cap may include directing the electromagnetic radiation into the cold cap effective to cause the cold cap to have a selected temperature profile. The selected temperature profile may include a temperature at the upper surface of the cold cap that is below the volatilization temperature of the hot material (e.g., waste material therein). The selected temperature profile may include a temperature at the interface of the calcined portion and the molten portion of the hot material (e.g., waste material therein) that is higher than the temperature where the electromagnetic radiation is not emitted therein.

The acts of the example method 200 may be effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap without causing emissions of one or more components of the hot material in the cold cap to exceed a selected level. For example, producing electromagnetic radiation outside of a processing chamber and directing the electromagnetic radiation into the cold cap of the hot material may be effective to cause the electromagnetic radiation to heat the calcined portion without heating the solid portion to a temperature in excess of a vaporization temperature of the one or more components (e.g., barium, cesium, iodine, strontium, technetium, xenon, etc.) of the hot material.

In examples, the method 200 may include adding hot material into the processing chamber. Adding hot material into the processing chamber may include adding any of the hot materials disclosed herein into the processing chamber via a waste inlet operably coupled thereto. The hot material may include one or more of waste particles (e.g., radioactive waste particles), dissolving agents (e.g., acids), glass particles, or dissolved particles of any of the foregoing. For example, adding hot material into the processing chamber may include adding radioactive waste particles and glass particles into the processing chamber via a waste inlet operably coupled thereto, such as in a slurry.

In examples, the hot material (e.g., slurry waste feed stream) may be fed spatially in a predefined pattern so that the directed electromagnetic radiation is aimed at a dry section of the cold cap to ensure the additional heating effect of the electromagnetic radiation is at the interface between the cold cap and the molten portion (e.g., molten glass surface).

In examples, adding hot material into the processing chamber may include adding hot material into the processing chamber so as to vary the thickness of the cold cap and thus vary the ratio of the radiation penetration depth to the cold cap thickness. The cold cap thickness could be controlled so as to achieve a selected ratio of radiation penetration depth to thickness for a given power and/or frequency. For a selected ratio this could enable selecting the power and/or frequency of the electromagnetic radiation so as to meet objectives that could include availability and cost of the electromagnetic radiation source and ease of transmitting and collimating the radiation. The ratio of the radiation penetration depth to cold cap thickness could be chosen so as to achieve a selected hot material processing (e.g., vitrification) rate or meet some other objective while limiting or eliminating emissions from the surface of the cold cap that faces the plenum.

In examples, the method 200 may include determining a temperature of the cold cap with one or more sensors. In some examples, determining the temperature of the cold cap with one or more sensors may include determining the temperature of the cold cap or materials emitted therefrom. In some examples, the method 200 may include adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to determining the temperature. For example, adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to determining the temperature may include adjusting one or more of the power or the frequency of the electromagnetic radiation to cause the cold cap to exhibit a selected temperature profile, a vitrification rate of the hot material (e.g., the waste material therein), or a selected penetration depth.

In examples, the method 200 may include drying the slurry. In some examples, the method 200 may include calcining the dried slurry. In some examples, the method 200 may include melting the calcined and dried slurry. In some examples, the method 200 may include pre-drying the hot material (e.g., radioactive waste slurry). Such pre-drying may allow selective adjustment of the penetration length of the electromagnetic radiation at a selected power and/or frequency.

In examples, the method 200 may include collimating the electromagnetic radiation with one or more of a phased array or a radiative horn. Collimating the electromagnetic radiation with one or more of the phased array or the radiative horn may include collimating the electromagnetic radiation into one or more beams of a selected width. Collimating the electromagnetic radiation with one or more of the phased array or the radiative horn may include directing the collimated beam in one or more directions in the processing chamber 110. Collimating the electromagnetic radiation with one or more of the phased array or the radiative horn may include collimating the electromagnetic radiation effective to cause the electromagnetic radiation into the cold cap to a selected depth.

The collimation of the electromagnetic radiation may allow use of the example systems and methods herein in cold crucible batch processing. In some examples, the sole source of heating of the hot material may be the electromagnetic radiation from the electromagnetic radiation source. For example, the longer penetration length of microwaves relative to millimeter wave radiation may allow examples, where electromagnetic radiation is the only form of heating in the system 200.

In examples, the method 200 may include joule heating the hot material in the processing chamber. In some examples, the method 200 may include induction heating the hot material in the processing chamber. In embodiments, heating the hot material in the processing chamber may include controlling one or more joule heaters or induction heaters to control the temperature of the hot material, such as to exhibit a selected temperature profile in the cold cap or process the hot material at a selected rate. In some examples, the method 200 may include heating the molten portion via one or more of joule heating or induction heating, wherein the power (e.g., heating energy) supplied by the electromagnetic radiation is less than the power (e.g., heating energy) supplied by the joule heating or induction heating. For example, the power applied to joule heating electrodes of a joule heated melter may be in a range of 100 kW to 3,000 kW and the power applied to the electromagnetic radiation source may be 20 kW to 600 kW (or about 4 kW to 150 kW). In some examples, the power applied to induction heating elements of in induction heating melter may be in a range of 10 kW to 200 kW and the power applied to the electromagnetic radiation source may be 2 kW to 40 kW (or about 0.5 kW to 10 kW).

In examples, the method 200 may include controlling one or more characteristics of the electromagnetic radiation (e.g., microwave radiation), such as with one or more of the controller, the electromagnetic radiation source, the one or more waveguides, or the one or more collimating devices. These characteristics may include one or more of power, frequency, or spatial location (e.g., depth or lateral location) of the electromagnetic radiation. In some examples, controlling one or more characteristics of the electromagnetic radiation may be responsive to sensor information detected by one or more sensors. The sensor information may include measurement of the temperature of the cold cap or emissions from heating of the surface of the molten material. In some examples, controlling one or more characteristics of the electromagnetic radiation may include directing the electromagnetic radiation to one or more locations (e.g., laterally or to a depth) that have not been treated with electromagnetic radiation (e.g., for a selected amount of time). Accordingly, controlling the one or more characteristics of the electromagnetic radiation may include varying one or more of the location, the frequency, or the power of the electromagnetic radiation over a selected duration of time, such as continuously or intermittently.

In some examples, the method 200 may include varying the frequency of the electromagnetic radiation, such as with the controller. In some examples, the method 200 may include adjusting one or more of the power or the frequency of the electromagnetic radiation to achieve a selected temperature profile in the cold cap. In some examples, the method 200 may include adjusting one or more of the power or the frequency of the electromagnetic radiation to a power or frequency that is effective to provide a selected electromagnetic radiation penetration depth into the cold cap. In some examples, the selected electromagnetic radiation penetration depth into the cold cap may be to the calcined portion or the interface between the calcined portion and the molten portion.

Using adjustable frequency radiation, it is possible to tune the adsorption of energy in the cold cap so that it is absorbed throughout the cold cap, thus enhancing the overall kinetics of the drying, calcining, and melting process as materials move from the surface of the cold cap to the interface of the cold cap with the molten portion. Such control of electromagnetic radiation may provide significant melt rate enhancement without heating the surface of the cold cap to a temperature where unwanted volatilization of constituents of the hot material (e.g., waste) would occur. The frequency of the electromagnetic radiation could be chosen so as to achieve different objectives or a combination of these objectives. One objective may be to produce a certain temperature profile (e.g., temperature as a function of distance from the interface between molten material and the cold cap) and average temperature in the cold cap. Another objective may be to achieve a selected processing rate. An additional objective may be to reduce reflection.

The control system can also be used to control the material feed rate based on information from sensors, such as temperature or emissions.

FIG. 3 is flow chart of a method 300 for melting a material, according to an embodiment. The method 300 includes an act 310 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, wherein the cold cap includes a solid portion that is uppermost in the cold cap and a calcined portion disposed between the solid portion and the molten portion, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz. The method 300 includes the act 320 of guiding the electromagnetic radiation into the processing chamber. The method 300 includes the act 330 of directing the electromagnetic radiation into the calcined portion of the cold cap. The method 300 includes the act 340 of sensing a temperature of the cold cap. The method 300 includes the act 350 of adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to the temperature of the cold cap. The method 300 may be carried out using any of the examples of systems disclosed herein.

The method 300 includes an act 310 of producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, wherein the cold cap includes a solid portion that is uppermost in the cold cap and a calcined portion disposed between the solid portion and the molten portion, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz may be similar or identical to the act 210 described above, in one or more aspects. For example, the act 310 may include producing electromagnetic radiation with any suitable electromagnetic radiation generator device such as a microwave radiation generator.

The electromagnetic radiation generator may be located outside of the processing chamber as described above with respect to FIG. 1. In some examples, producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, wherein the cold cap includes a solid portion that is uppermost in the cold cap and a calcined portion disposed between the solid portion and the molten portion, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz may include producing electromagnetic radiation with any of the frequencies or power levels disclosed herein. The act 310 may include varying one or more of the power or the frequency of the electromagnetic radiation over a duration. For example, producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein may include producing electromagnetic radiation with a varying frequency between 0.9 GHz and 10 GHz or a varying power between 1 kW and 700 kW.

In examples, producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz, is effective to cause the electromagnetic radiation to heat the calcined portion of the cold cap without heating the solid portion to a temperature in excess of a vaporization temperature of the hot material (e.g., the waste material or glass particles therein).

The method 300 includes the act 320 of guiding the electromagnetic radiation into the processing chamber. The act 320 of guiding the electromagnetic radiation into the processing chamber may include using one or more waveguides to guide the electromagnetic radiation into the processing chamber. For example, the act 320 may include using any of the waveguides disclosed herein to guide the electromagnetic radiation from the electromagnetic radiation source to the interior region of the processing chamber. In some examples, guiding the electromagnetic radiation into the processing chamber may include using a plurality of waveguides to guide the electromagnetic radiation into the processing chamber.

The method 300 includes the act 330 of directing the electromagnetic radiation into the calcined portion of the cold cap. Directing the electromagnetic radiation into the calcined portion of the cold cap may include producing a localized beam of electromagnetic radiation in the processing chamber. In some examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing varying frequencies of electromagnetic radiation into the hot material over a duration. Directing the electromagnetic radiation into the calcined portion of the cold cap may include directing the electromagnetic radiation using one or more collimating devices. The one or more collimating devices may include one or more horns or one or more phased arrays. In some examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing the electromagnetic radiation into the cold cap without causing volatilization of the hot material in the cold cap. For example, one or more collimating devices may be operably coupled to the waveguides operably coupled to the electromagnetic radiation generator and protrude to (e.g., into) the interior region of the processing chamber. In some examples, the act 330 may include collimating the electromagnetic radiation with one or more of a phased array or a radiative horn. Collimating the electromagnetic radiation may include collimating the electromagnetic radiation into one or more beams of a selected width. Collimating the electromagnetic radiation may include directing the collimated beam in one or more directions in the processing chamber. Collimating the electromagnetic radiation may include collimating the electromagnetic radiation effective to cause the electromagnetic radiation into the cold cap to a selected depth.

In examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing the electromagnetic radiation into the cold cap without causing volatilization of the hot material in the cold cap. For example, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing the electromagnetic radiation to the interface between the calcined portion and the molten portion of the hot material in the processing chamber.

In examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing the electromagnetic radiation into cold cap effective to cause the cold cap to have a selected temperature profile. The selected temperature profile may include a temperature at the upper surface of the cold cap that is below the volatilization temperature of the hot material (e.g., radioactive waste material therein). The selected temperature profile may include a temperature at the interface of the calcined portion and the molten portion of the hot material that is higher than the temperature where the electromagnetic radiation is not emitted therein.

In examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include moving the location of the electromagnetic radiation in the cold cap, such as to a different lateral location or penetration depth, with the one or more collimating devices. For example, directing the electromagnetic radiation into the calcined portion of the cold cap may include continuously or intermittently moving the electromagnetic radiation over a duration. In some examples, directing the electromagnetic radiation into the calcined portion of the cold cap may include directing or altering a target location of the electromagnetic radiation with the controller, such as responsive to one or more temperature measurements of the hot material (e.g., cold cap).

The method 300 includes the act 340 of sensing a temperature of the cold cap. In some examples, sensing a temperature of the cold cap may include sensing the temperature of the cold cap with one or more sensors. The one or more sensors may be similar or identical to any of the sensors disclosed herein. In some examples, sensing a temperature of the cold cap may include determining the temperature of the cold cap or materials (e.g., cesium or technetium) emitted therefrom. In some examples, sensing a temperature of the cold cap may include sensing the temperature of the cold cap with an infrared scanning thermometer or a thermocouple. The sensed temperature may be used to selectively control one or more aspects of the operation of the system, such as controlling (adjusting or varying) the frequency of the electromagnetic radiation, the rate of addition of hot material into the processing chamber, the rate of removal of the molten material from the processing chamber, the heat added by the joule electrodes, the heat added by an induction heater (e.g., power applied to one or more induction heating elements), or the target location of the electromagnetic radiation in the cold cap.

The method 300 includes the act 350 of adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to the temperature of the cold cap. In some examples, adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to determining the temperature of the cold cap may include increasing or decreasing the frequency of the electromagnetic radiation to achieve a selected penetration depth. The penetration depth may be adjusted to increase heat at the interface between the cold cap and the molten material. In some examples, adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to the temperature of the cold cap may include adjusting the power or the frequency of the electromagnetic radiation to cause the cold cap to exhibit a selected temperature profile, a vitrification rate of the hot material (e.g., the waste material therein), or a selected penetration depth. In some examples, adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to determining the temperature may include continuously or intermittently adjusting the power or frequency of the electromagnetic radiation over a duration. In some examples, adjusting the power or frequency of the electromagnetic radiation may be responsive to pre-drying of the radioactive material.

In embodiments, adjusting one or more of the power or the frequency of the electromagnetic radiation responsive to determining the temperature may include using the controller to adjust the power or the frequency. For example, the controller may receive as input, the sensed temperature of the cold cap or amount of component(s) of the hot material in the gas phase and responsive thereto provide instructions to the electromagnetic radiation source to alter the electromagnetic radiation to a selected power or frequency. The controller may adjust the power or the frequency based upon one or more parameters, such as electromagnetic power or frequency, depth of penetration, hot material composition, selected emission level, selected processing rate, amount of pre-drying of the material before it is introduced to the cold cap, spatial positioning, molten material temperature, or selected cold cap temperature. The controller may utilize closed loop or real time monitoring of any parameters and or/open loop control using a look-up table. The look-up table can make use of experimental measurements of the impact of electromagnetic power or frequency or any other parameters on processing rate enhancement, emissions from the cold cap, or other characteristics of processing the hot material. The controller may adjust one or more of the frequency of electromagnetic radiation, the power of electromagnetic radiation (or supplied to the electromagnetic radiation source), the feed rate of hot material into the processing chamber, the power applied to the joule electrodes or the induction coil to maintain or adjust the temperature of the cold cap (e.g., surface temperature or average temperature) to above or below a selected temperature or below a selected emission level.

The method 300 may be used to process radioactive material. For example, the processing chamber may be configured to contain radioactive material and the hot material includes radioactive material. In such examples, the electromagnetic radiation frequency may be selected to penetrate the radioactive (waste) material, such as to a selected depth or through the cold cap.

In examples, the method 300 may include directing the electromagnetic radiation responsive to material emissions from the cold cap. For example, the system 100 (FIG. 1) may include one or more sensors for detecting emission of the material from the cold cap, such as a Geiger counters or one or more spectrometers (not shown) disposed in a gaseous component outlet (not shown) of the processing chamber. In such examples, detected material emissions or an amount thereof from the cold cap can be used to monitor and limit radioactive material emissions from the melting process to below selected levels.

In examples, the method 300 may include any acts or aspects of the method 200. For example, the method 300 may include an adding hot material into the processing chamber as disclosed above with respect to the method 200. The hot material may include one or more of radioactive waste particles, dissolving agents, glass particles, or dissolved particles of any of the foregoing. For example, adding hot material into the processing chamber may include adding radioactive waste particles and glass particles into the processing chamber via a waste inlet operably coupled thereto, such as in a slurry. In some examples, adding hot material into the processing chamber may include adding radioactive waste particles and glass particles into the processing chamber at a rate selected to maintain an amount of radioactive material in the melter below a selected value (e.g., keep the molten portion and cold cap below one half, one third, or one quarter of the volume of the processing chamber. In some examples, the amount of radioactive material may be limited to avoid critical mass of the radioactive material.

In some examples, the method 300 may include drying or pre-drying (e.g., dewatering) the hot material, such as drying the slurry of hot material. In some examples, the hot material may be fed spatially in a predefined pattern so that the directed electromagnetic radiation is focused on a dry section of the cold cap to ensure the additional heating effect of the electromagnetic radiation is at the interface between the cold cap and the molten portion. In some examples, adding hot material into the processing chamber may include adding hot material into the processing chamber to achieve one or more processing properties or characteristics.

In some examples, the method 300 may include joule heating the hot material in the processing chamber as disclosed above with respect to the method 200. In some examples, the method 300 may include controlling one or more characteristics of the electromagnetic radiation (e.g., microwave radiation), such as with one or more of the controller, the electromagnetic radiation source, the one or more waveguides, or the one or more collimating devices as disclosed above with respect to the method 200. For example, the method 300 may include varying the frequency of the electromagnetic radiation. Controlling one or more characteristics of the electromagnetic radiation may be effective to control one or more characteristics of the hot material in the processing chamber or the processing characteristics.

In some examples, example systems disclosed herein may be implemented in mobile apparatus. For example, use of mobile systems (e.g., waste melters) that may allow onsite immobilization of radioactive material resulting from medical use, nuclear power production, a nuclear reactor accident, or malicious use radioactive material.

FIG. 4 is a schematic of a mobile system 400, according to an embodiment. The mobile system 400 may include a carriage 404 for supporting and moving a processing chamber 410, an electromagnetic radiation source 120, a controller 140, or any other components of the mobile system 400. The mobile system 400 may include the carriage 404 that has wheels 408 for moving the mobile system 400 from one location to another. The carriage 404 may include a frame having a plurality of legs 405 and a table 407 disposed on the legs 405. The table 407 may include one or more cross members positioned to support one or more components of the mobile system 400. The frame of the carriage 404 may include one or more cross-members or connections positioned to support the processing chamber 410.

The carriage 404 includes the wheels 408 at the end of the legs 405. In some examples, the carriage may include skids or tracks in addition or alternative to the wheels 408. In some examples, the carriage 404 may include a drive mechanism (e.g., motor, transmission, drive shafts, axles, etc.). In some examples, the carriage 404 may have a connection (e.g., hitch) that allows the carriage 404 to be towed by a vehicle.

The mobile system 400 may include one or more components of the system 100. For example, the mobile system 400 may include the processing chamber 410, which may be similar or identical to the processing chamber 110 in one or more aspects. The processing chamber 410 may have any dimensions such as a relatively shallow container (e.g., 1 cm to 15 cm maximum depth) or a relatively deep container. The relatively shallow container may allow faster processing of materials using solely electromagnetic heating and may prevent critical mass of radioactive materials therein (and prevent and associated critical nuclear event). The processing chamber 410 may contain hot material 132 therein. The processing chamber 410 may be sealed to contain the hot material 132 and fluids therein in a closed environment. In some examples, the processing chamber 410 may be operably coupled to a hot material 132 (e.g., radioactive waste feed slurry) supply via the inlet 155.

The mobile system 400 includes the electromagnetic radiation source 120. The electromagnetic radiation source 120 may be supported by the carriage 404. The electromagnetic radiation source 120 may be disposed outside of the processing chamber 410, such as outside of a containment structure (not shown) around the processing chamber 410 or between the processing chamber 410 and the electromagnetic radiation source 120. The containment structure may be similar or identical to the containment structure 190 (FIG. 1) in one or more aspects, such as having a cladding or shielding to contain one or more emissions from the processing chamber 410. The electromagnetic radiation source 120 may be shielded from emissions (e.g., radiation and/or heat) from the material in the processing chamber 410. The electromagnetic radiation source 120 may be operably coupled to the one or more waveguides 122 which may be operably coupled to the one or more collimating devices 124. The electromagnetic radiation source 120, the one or more waveguides 122, and the one or more collimating devices 124 may be positioned to emit the electromagnetic radiation 125 into the cold cap 134, through the solid portion 136 and calcined portion 138 to the interface between the molten portion 139 of the hot material 132 as described herein.

The mobile system 400 may include the gas vent 175 operably coupled to the processing chamber 410. The gas vent 175 may be operably coupled to one or more gas cleaning apparatuses as described herein. The one or more gas cleaning apparatuses may be used to clean the gas emitted from the processing chamber 410, such as removing radioactive material therefrom or encapsulating radioactive material therein. A moveable containment structure in which the processing would occur might also be used. The containment structure may be similar or identical to the containment structure 190 disclosed herein. Such a containment structure may include off gas treatment systems such as scrubbers, etc., disposed therein or thereon.

The processing chamber 410 may include an outlet 170, such as in a lower portion of the processing chamber. The outlet 170 may be used to remove molten portion 139 (e.g., vitrified radioactive waste) from the processing chamber 410.

The mobile system 400 may include the controller 140. The controller 140 may be operably coupled to one or more of any of the components of the mobile system 400. The controller 140 may include programming stored therein to automatically direct and control any aspects of operation of the mobile system 400. For example, the controller 140 may be operably coupled to the electromagnetic radiation source 120 and may selectively control the initiation and frequency of the electromagnetic radiation produced therein. In some examples, the controller 140 may be configured to a drive system (not shown) on the carriage 404 to control movement of the mobile system 400. The controller 140 may be used to control the mobile system according to any of the example methods disclosed herein, in one or more aspects.

The mobile system 400 may include one or more sensors (not shown) for measuring the temperature of the hot material (e.g., cold cap 134) measuring emissions from the hot material (e.g., volatilized radioactive material), as disclosed herein with respect to the sensors 150.

In some examples, the sole source of heating the in processing chamber 410 may be from the electromagnetic radiation 125. In some examples, the mobile system 400 may include one or more of joule electrodes or induction heating elements, as disclosed herein with respect to the system 100, to heat the hot material therein.

The mobile system 400 may include a power source (not shown). The power source may be operably coupled to any of the components of the mobile system 400 to supply electrical energy thereto. The power source may include at least one of a motor, generator, batteries, solar cells, or any other source of electrical energy. For example, the power source may include an internal combustion engine positioned and attached to the carriage 404 to move the carriage 404. The power source may include an alternator or generator operably coupled to, and powered by, the motor.

The mobile system 400 may be used to provide local waste processing at different sites, such as the department of energy Hanford site, or any nuclear power plant or waste site.

Any of the example systems disclosed herein may be used to carry out any of the example methods disclosed herein, such as using a controller. FIG. 5 is a schematic of a controller 500 for executing any of the example methods disclosed herein, according to an embodiment. The controller 500 may be configured to implement any of the example methods disclosed herein, such as the method 200 or 300. The controller 500 includes at least one computing device 510. The at least one computing device 510 is an exemplary computing device that may be configured to perform one or more of the acts described above, such as the method 200 or 300. The at least one computing device 510 can include one or more servers, one or more computers (e.g., desk-top computer, lap-top computer), or one or more mobile computing devices (e.g., smartphone, tablet, etc.). The computing device 510 can comprise at least one processor 520, memory 530, a storage device 540, an input/output (“I/O”) device/interface 550, and a communication interface 560. While an example computing device 510 is shown in FIG. 5, the components illustrated in FIG. 5 are not intended to be limiting of the controller 500 or computing device 510. Additional or alternative components may be used in some examples. Further, in some examples, the controller 500 or the computing device 510 can include fewer components than those shown in FIG. 5. For example, the controller 500 may not include the one or more additional computing devices 512. In some examples, the at least one computing device 510 may include a plurality of computing devices, such as a server farm, computational network, or cluster of computing devices. Components of computing device 510 shown in FIG. 5 are described in additional detail below.

In some examples, the processor(s) 520 includes hardware for executing instructions (e.g., adjusting power or frequency of electromagnetic radiation), such as those making up a computer program. For example, to execute instructions, the processor(s) 520 may retrieve (or fetch) the instructions from an internal register, an internal cache, the memory 530, or a storage device 540 and decode and execute them. In particular examples, processor(s) 520 may include one or more internal caches for data such as look-up tables. As an example, the processor(s) 520 may include one or more instruction caches, one or more data caches, and one or more translation lookaside buffers (TLBs). Instructions in the instruction caches may be copies of instructions in memory 530 or storage device 540. In some examples, the processor 520 may be configured (e.g., include programming stored thereon or executed thereby) to carry out one or more portions of any of the example methods disclosed herein.

In some examples, the processor 520 is configured to perform any of the acts disclosed herein such as in method 200 or 300 or cause one or more portions of the computing device 510 or controller 500 to perform at least one of the acts disclosed herein. Such configuration can include one or more operational programs (e.g., computer program products) that are executable by the at least one processor 520. For example, the processor 520 may be configured to automatically adjust one or more of the power or frequency of the electromagnetic radiation responsive to a sensed temperature or level (e.g., rate) of emission of one or more components of the hot material.

The at least one computing device 510 (e.g., a server) may include at least one memory storage medium (e.g., memory 530 and/or storage device 540). The computing device 510 may include memory 530, which is operably coupled to the processor(s) 520. The memory 530 may be used for storing data, metadata, and programs for execution by the processor(s) 520. The memory 530 may include one or more of volatile and non-volatile memories, such as Random Access Memory (RAM), Read Only Memory (ROM), a solid state disk (SSD), Flash, Phase Change Memory (PCM), or other types of data storage. The memory 530 may be internal or distributed memory.

The computing device 510 may include the storage device 540 having storage for storing data or instructions. The storage device 540 may be operably coupled to the at least one processor 520. In some examples, the storage device 540 can comprise a non-transitory memory storage medium, such as any of those described above. The storage device 540 (e.g., non-transitory storage medium) may include a hard disk drive (HDD), a floppy disk drive, flash memory, an optical disc, a magneto-optical disc, magnetic tape, or a Universal Serial Bus (USB) drive or a combination of two or more of these. Storage device 540 may include removable or non-removable (or fixed) media. Storage device 540 may be internal or external to the computing device 510. In some examples, storage device 540 may include non-volatile, solid-state memory. In some examples, storage device 540 may include read-only memory (ROM). Where appropriate, this ROM may be mask programmed ROM, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), electrically alterable ROM (EAROM), or flash memory or a combination of two or more of these. In some examples, one or more portions of the memory 530 and/or storage device 540 (e.g., memory storage medium(s)) may store one or more databases thereon. At least some of the databases may be used to store one or more of look-up tables, operation programs, threshold levels of components in gas phase, correlations of frequencies or power levels to materials in hot materials or thicknesses thereof, etc., as disclosed herein.

In some examples, one or more of look-up tables, operation programs, threshold levels of components in gas phase, correlations of frequencies or power levels to materials in hot materials or thicknesses thereof, etc., may be stored in a memory storage medium such as one or more of the at least one processor 520 (e.g., internal cache of the processor), memory 530, or the storage device 540. In some examples, the at least one processor 520 may be configured to access (e.g., via bus 570) the memory storage medium(s) such as one or more of the memory 530 or the storage device 540. For example, the at least one processor 520 may receive and store the data (e.g., look-up tables) as a plurality of data points in the memory storage medium(s). The at least one processor 520 may execute programming stored therein adapted access the data in the memory storage medium(s) to automatically adjust the power or frequency of the electromagnetic radiation. For example, the at least one processor 520 may access one or more look-up tables in the memory storage medium(s) such as memory 530 or storage device 540.

The computing device 510 also includes one or more I/O devices/interfaces 550, which are provided to allow a user to provide input to, receive output from, and otherwise transfer data to and from the computing device 510. These I/O devices/interfaces 550 may include a mouse, keypad or a keyboard, a touch screen, camera, optical scanner, network interface, web-based access, modem, a port, other known I/O devices or a combination of such I/O devices/interfaces 550. The touch screen may be activated with a stylus or a finger.

The I/O devices/interfaces 550 may include one or more devices for presenting output to a user, including, but not limited to, a graphics engine, a display (e.g., a display screen or monitor), one or more output drivers (e.g., display drivers), one or more audio speakers, and one or more audio drivers. In certain examples, I/O devices/interfaces 550 are configured to provide graphical data to a display for presentation to a user. The graphical data may be representative of one or more graphical user interfaces and/or any other graphical content as may serve a particular implementation.

The computing device 510 can further include a communication interface 560. The communication interface 560 can include hardware, software, or both. The communication interface 560 can provide one or more interfaces for communication (such as, for example, packet-based communication) between the computing device 510 and one or more additional computing devices 512 or one or more networks. For example, communication interface 560 may include a network interface controller (NIC) or network adapter for communicating with an Ethernet or other wire-based network or a wireless NIC (WNIC) or wireless adapter for communicating with a wireless network, such as a WI-FI.

Any suitable network and any suitable communication interface 560 may be used. For example, computing device 510 may communicate with an ad hoc network, a personal area network (PAN), a local area network (LAN), a wide area network (WAN), a metropolitan area network (MAN), or one or more portions of the Internet or a combination of two or more of these. One or more portions of one or more of these networks may be wired or wireless. As an example, one or more portions of controller 500 or computing device 510 may communicate with a wireless PAN (WPAN) (such as, for example, a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network, a cellular telephone network (such as, for example, a Global System for Mobile Communications (GSM) network), or other suitable wireless network or a combination thereof. Computing device 510 may include any suitable communication interface 560 for any of these networks, where appropriate.

The computing device 510 may include a bus 570. The bus 570 can include hardware, software, or both that couples components of computing device 510 to each other. For example, bus 570 may include an Accelerated Graphics Port (AGP) or other graphics bus, an Enhanced Industry Standard Architecture (EISA) bus, a front-side bus (FSB), a HYPERTRANSPORT (HT) interconnect, an Industry Standard Architecture (ISA) bus, an INFINIBAND interconnect, a low-pin-count (LPC) bus, a memory bus, a Micro Channel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCIe) bus, a serial advanced technology attachment (SATA) bus, a Video Electronics Standards Association local (VLB) bus, or another suitable bus or a combination thereof.

It should be appreciated that any of the examples of acts described herein, such as in the method 200 or 300 may be performed by and/or at the computing device 510.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. 

What is claimed is:
 1. A system, comprising: a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid; an electromagnetic radiation source located outside of the processing chamber and configured to selectively generate electromagnetic radiation with a frequency between 0.9 GHz and 10 GHz; one or more waveguides operably coupled to the electromagnetic radiation source and configured to guide the electromagnetic radiation into the cold cap of the hot material in the processing chamber; a controller operably coupled to the electromagnetic radiation source, wherein the controller is configured to selectively adjust one or more of a power or the frequency of the electromagnetic radiation to selectively control a temperature profile in the cold cap while preventing emissions of volatile components from the cold cap from exceeding a selected level; and at least one of one or more sensors positioned and configured to sense a temperature of the cold cap or measure emissions from a surface of the cold cap; wherein the controller is configured to receive a sensed temperature of the cold cap and in response thereto, selectively adjust the power of the electromagnetic radiation.
 2. The system of claim 1, further comprising one or more collimating devices operably coupled to the one or more waveguides, wherein the one or more collimating devices are configured to collimate the electromagnetic radiation.
 3. The system of claim 2, wherein the one or more collimating devices includes one or more phased arrays configured to collimate the electromagnetic radiation.
 4. The system of claim 1, wherein the controller is configured to receive the sensed temperature of the cold cap and in response thereto, selectively adjust the frequency of the electromagnetic radiation emitted from the electromagnetic radiation source.
 5. The system of claim 1, wherein the controller is configured to control a pre-drying of the hot material that is introduced into the processing chamber based on one or more of the sensed temperature or emissions of the cold cap detected by the one or more sensors.
 6. The system of claim 1, wherein at least another sensor of the at least one or more sensors positioned to measure a volatile material in gases emitted from the processing chamber, wherein the volatile material includes cesium or technetium.
 7. The system of claim 1, further comprising one or more joule heating electrodes positioned and configured to heat the molten portion.
 8. The system of claim 1, further comprising one or more induction heating elements positioned and configured to heat the molten portion.
 9. The system of claim 1, wherein the electromagnetic radiation source is the only means of heating the hot material.
 10. The system of claim 1, wherein a maximum depth of the molten portion is less than 15 cm.
 11. The system of claim 1, wherein the electromagnetic radiation source is configured to emit the electromagnetic radiation at a frequency and power effective produce a penetration depth of the electromagnetic radiation into the cold cap of 1 cm to 15 cm.
 12. The system of claim 1, wherein the controller is configured to alter the frequency of the electromagnetic radiation to provide a selected temperature profile in the cold cap.
 13. The system of claim 1, wherein: the processing chamber is configured to contain radioactive material; and the hot material includes radioactive material.
 14. A method for melting material, the method comprising: producing electromagnetic radiation outside of a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid, and wherein a frequency of the electromagnetic radiation is between 0.9 GHz and 10 GHz; directing the electromagnetic radiation into the cold cap; and adding hot material into the processing chamber, wherein the hot material includes radioactive waste particles and glass particles; and wherein adding the hot material into the processing chamber includes adding the hot material via a waste inlet operably coupled to the processing chamber; wherein producing the electromagnetic radiation outside of the processing chamber and directing the electromagnetic radiation into the cold cap are effective to heat the hot material in the cold cap to a selected temperature profile within the cold cap without causing emissions of one or more components of the hot material in the cold cap to exceed a selected level; and wherein the cold cap includes a solid portion that is uppermost in the cold cap and a calcined portion disposed between the solid portion and the molten portion.
 15. The method of claim 14, further comprising varying the frequency of the electromagnetic radiation.
 16. The method of claim 14, further comprising adjusting the frequency of the electromagnetic radiation to achieve the selected temperature profile in the cold cap.
 17. The method of claim 14, wherein: producing electromagnetic radiation outside of the processing chamber and directing the electromagnetic radiation into the cold cap of the hot material are effective to cause the electromagnetic radiation to heat the calcined portion without heating the solid portion to a temperature in excess of a vaporization temperature of the one or more components of the hot material.
 18. The method of claim 14, wherein the frequency is effective to provide a selected electromagnetic radiation penetration depth into the cold cap.
 19. The method of claim 14, further comprising: determining a temperature of the cold cap with one or more sensors; and adjusting the frequency of the electromagnetic radiation responsive to determining the temperature.
 20. The method of claim 14, further comprising heating the molten portion via one or more of joule heating or induction heating, wherein a first amount of power supplied by the electromagnetic radiation is less than a second amount of power supplied by the joule heating or induction heating.
 21. A system, comprising: a processing chamber configured to hold hot material therein, wherein the hot material includes a molten portion and a cold cap that is disposed on the molten portion and is at least semi-solid; an electromagnetic radiation source located outside of the processing chamber and configured to selectively generate electromagnetic radiation with a frequency between 0.9 GHz and 10 GHz; one or more waveguides operably coupled to the electromagnetic radiation source and configured to guide the electromagnetic radiation into the cold cap of the hot material in the processing chamber; a controller operably coupled to the electromagnetic radiation source, wherein the controller is configured to selectively adjust one or more of a power or the frequency of the electromagnetic radiation to selectively control a temperature profile in the cold cap while preventing emissions of volatile components from the cold cap from exceeding a selected level; and at least one of one or more sensors positioned and configured to sense a temperature of the cold cap or measure emissions from a surface of the cold cap; wherein the controller is configured to receive a sensed temperature of the cold cap and in response thereto, selectively adjust the power of the electromagnetic radiation; and wherein the system is mobile.
 22. The system of claim 21, wherein the electromagnetic radiation source using the frequency between 0.9 and 10 GHz is the sole heating source.
 23. The system of claim 21, wherein the hot material includes radioactive material.
 24. The system of claim 21, wherein a depth of molten material is between 1 and 15 cm. 